Effects of home nest odors on black-white preference in the developing rat: implications for developmental learning research.

Developing animals 17 and 30 days of age were tested for black-white preference in the presence of either clean shavings or soiled bedding material from the home cage. Home nest shavings markedly reduced dark preference in 17-day-old rats but had no effect on dark preference in 30-day-old rats. Because many developmental studies have used two-compartment, black and white chambers to study the effects of familiar home nest shavings on learning and memory, it may be that differential preference for black influenced the results obtained. The apparent alleviation of learning and memory deficits produced by the presence of home nest shavings may have been the result of changes in black-white preference rather than differences in learning and memory per se. Similar influences may underlie the effects of home nest stimuli on other learning tasks such as spatial alternation.